Considerations for low-embodied carbon glazing design and specification
While product-specific Environmental Product Declarations (EPDs) can be valuable tools, it is very important to understand what their data means, and how and when to use it to make sound carbon-based decisions. In the case of glazing, do not compare EPDs from different insulated glass unit (IGU) or flat glass fabricators to make supplier selections. Instead, focus on the design and specification details to reduce the embodied carbon of the glazing in a project and minimize lifecycle impacts. Consider the following guidelines:
- Locally source aluminum: Ensure aluminum is sourced from North American providers with low-carbon intensive electricity supply and be efficient with its use.
- Focus on IGU durability and service life: Specify an IGU design and suppliers that will deliver insulating glass with the best quality and in-service durability. Avoiding a “lowest bidder wins” approach to contracting supports this goal by allowing fabricators to invest in higher quality materials and focus on quality production.
- Assess the lifecycle value of triple pane versus double pane: Does the operational emissions benefit outweigh the embodied carbon impact? How many years before the operational energy savings offset the added embodied carbon? Can you reach the needed thermal performance specification with a dual-pane unit, warm-edge spacer and a high-performance thermally broken frame? Are there ways of reducing the impact of triple pane by using a thinner inboard lite?
- Design with efficiency in mind: Design facades with a view to helping fabricators reduce waste and improve efficiencies by, for example, reducing the number of unique sizes. Assess whether the glass is over-engineered. Do all IGUs in the façade need to use the same glass thickness that was specified for the largest units? Do all lites need heat treatment?
- Find alternative lower cost ways to allow your IGU fabricator partners to demonstrate their commitment to reducing the environmental impact of their operations, rather than requesting expensive EPDs (which provide a single snapshot in time).